This three-phase Small Business Innovation Research project addresses one the most significant problems in public health protection: monitoring of indoor air quality and controlling the ventilation systems in residential, office and industrial buildings. The development of a novel advanced microsensor for detecting gaseous formaldehyde in air is proposed. The sensing method utilizes the conductivity change induced, upon exposure to formaldehyde, in a layer of tin oxide. Cross-sensitivity to other volatile organic chemicals is eliminated by patterning of the tin oxide surface by an inert protecting layer with sub-nanometer pores, each shaped to selectively host a single formaldehyde molecule. Incorporation of this novel sensing material into a high-area nanostructured sensor platform will enable production of highly sensitive, selective, low-power, and low-cost formaldehyde microsensors. The Phase I project will demonstrate the feasibility of the proposed approach through fabrication of sensors and their comprehensive testing in conditions simulating contaminated indoor air. To ensure successful Phase II product development and Phase III commercialization, partnership has been secured with one of the leading developers of components and systems for energy applications. By combining coordination chemistry with nanotechnology and microfabrication, the proposed approach is likely to enable a novel family of low-cost highly sensitive and selective sensor systems for precise quantitative monitoring of human exposures to toxicants. Thus, the proposed research is highly relevant to the mission of the National Institute Of Environmental Health Sciences. [unreadable] [unreadable] Public Health Relevance: The project addresses one the most significant problems in public health protection: monitoring of indoor air quality and controlling the ventilation systems in residential, office, and industrial buildings. The development of novel advanced sensors for detecting formaldehyde - one of the most ubiquitous and dangerous for human health air contaminants - is proposed. The proposed technology will enable a novel family of high-performance and low-cost sensor systems for generating precise and quantitative measures of human exposure to harmful chemicals at the point of contact. [unreadable] [unreadable] [unreadable]